Had my D700 on manual with my 24-70 mm lens The first photo I took, camera did its thing - no problem. This photo was of a reflection in a water puddle

The 2nd time ( 1 min later) photographing the same item,
the shutter would not work - r 06 came up in the control Panel.

This error message is till there when endeavouring to taking any photo and the shutter does not work i e unable to push the shutter down

I would be grateful for some advice

thank you

sue